1. Field of the Invention
The present invention is directed to the preparation of 4,4'-dihydroxybiphenyl. More particularly, this invention involves the hydrolysis of 4,4'-dibromobiphenyl in the presence of a copper compound catalyst.
2. Description of the Prior Art
4,4'-Dihydroxybiphenyl is useful as an antioxidant for a resin, an intermediate for a dye and a starting material for polyesters, polyepoxides, polyurethanes and polycarbonates. It may also be used as a co-monomer in high performance polyester film, cable, rope and engineering plastics.
U.S. Pat. No. 4,340,768 teaches the production of 4,4'-dihydroxybiphenyl by hydrolyzing 4,4'-dibromobiphenyl in the presence of a copper compound catalyst in an aqueous solution, extracting by-products from the alkaline aqueous solution with an alcohol or ketone which forms an organic phase, neutralizing or acidifying the alkaline aqueous solution with an acid, extracting the reaction product with the alcohol or ketone and finally crystallizing the reaction product from the extracted solution. This process requires two extractions using an alcohol or ketone. The first extraction is designed to remove by-products impurities.
It has recently been discovered that by using a copper compound catalyst containing copper in the plus two oxidation state minimal by-products are formed in the hydrolysis reaction and lesser amounts of catalyst are required.